JP5513712B2 - Exhaust treatment device - Google Patents

Description

  The present invention relates to an exhaust treatment device for treating a gas (exhaust gas) discharged from a combustion device and containing various exhaust substances.

  Purifying the exhaust from the combustion device to suppress the spread of environmental pollution is an important issue. For example, in the case of a diesel combustion engine, PM (particulate matter: particulate matter = mainly black smoke) in the exhaust (Soot), to suppress the emission of unburned fuel called SOF and components of lubricating oil, components generated from sulfur in diesel fuel called sulfate, and other solid substances) to the atmosphere In addition, for example, a diesel particulate filter is installed in the exhaust passage, and exhaust gas is passed through the diesel particulate filter to collect PM in the exhaust, while various diesel particulate filters are used. Reproduction is performed by the method.

  Further, for example, in Patent Document 1, in order to realize simultaneous reduction of NOx and PM contained in exhaust gas, a diesel particulate filter and CSF are interposed in the exhaust passage, and NOx reduction is performed downstream thereof. It has been proposed to install an effective SCR (Selective Catalytic Reduction). Urea SCR is a selective reduction-type NOx catalyst that has the property of selectively reacting NOx with a reducing agent even in the presence of oxygen, and adds non-toxic urea water to the exhaust gas. It is thermally decomposed into ammonia and carbon dioxide, and the produced ammonia is used as a reducing agent to reduce and purify NOx in the exhaust gas on the selective reduction type NOx catalyst.

More specifically, in the conventional exhaust treatment apparatus as described in Patent Document 1, for example, as shown in FIG. 8, the exhaust temperature on the most upstream side of the exhaust passage 2 of the diesel combustion engine 1 is relatively high. From the viewpoint of regeneration efficiency and the like, an oxidation catalyst device 3 and a diesel particulate filter 4 are installed at a position, a urea water addition device 5 and a urea SCR catalyst device 6 are installed downstream thereof, and from the urea SCR catalyst device 6 An ammonia oxidation catalyst device 7 for oxidizing excess ammonia (NH ₃ ) leaking was interposed (oxidation catalyst device 3, urea water addition device 5, urea SCR catalyst device 6, ammonia oxidation) For the reaction in each device of the catalyst device 7, see Fig. 9. The hydrolysis reaction in Fig. 9 is represented by the following equation: Hydrolysis reaction formula: (NH ₂ ) ₂ CO + H ₂ O → 2NH ₃ + CO ₂ ).

  Here, the urea water injection nozzle 5A constituting the urea water addition device 5 is disposed on the exhaust upstream side of the urea SCR catalyst device 6, and the exhaust gas upstream of the urea SCR catalyst device 6 from the urea water injection portion of the urea injection nozzle 5A. The distance to the side end face needs to be relatively long in order to secure the time required for hydrolysis from urea to ammonia.

  Further, it is necessary to mix and diffuse the supplied urea and the exhaust well so that urea can be hydrolyzed well.

  From this point of view, conventionally, as shown in FIG. 8, the exhaust gas is discharged while taking a relatively long distance from the urea water injection portion of the urea water injection nozzle 5 </ b> A to the exhaust upstream end face of the urea SCR catalyst device 6. In order to promote the mixing by increasing the flow rate of the urea, the large-diameter housing case 8 for housing the oxidation catalyst device 3 and the diesel particulate filter 4 and the urea SCR catalyst device 6 and ammonia are provided upstream of the urea SCR catalyst device 6. A small-diameter exhaust passage 2A having a smaller exhaust passage cross-sectional area than the diameter of the large-diameter housing case 9 that houses the oxidation catalyst device 7 is provided, and the urea water injection nozzle 5A is attached thereto.

  Further, in order to mix the injected urea water and the exhaust gas well so as to perform the hydrolysis of urea well, a buffer is provided in the small diameter exhaust passage 2A on the exhaust downstream side of the urea water injection portion of the urea water injection nozzle 5A. A mixer composed of a plate or the like was arranged.

JP 2007-2697 A

  However, as shown in FIG. 8, the cross-sectional area is reduced to be smaller than the diameter of the housing case 8 that houses the oxidation catalyst device 3 and the diesel particulate filter 4 and the diameter of the housing case 9 that houses the urea SCR catalyst device 6. When the exhaust passage 2A having a small diameter is provided and the urea water injection nozzle 5A is attached to the exhaust passage 2A, the pressure loss is increased.

  For this reason, the diameter difference between the large-diameter housing cases 8 and 9 and the small-diameter exhaust passage 2A has been devised in shape such as taper or butting, but it is possible to reduce pressure loss and achieve good mixing / The fact is that it is difficult to achieve both the diffusion action and the sufficient effect has not been obtained.

  The present invention has been made in view of such circumstances, and while being a simple, compact and inexpensive configuration, the reducing agent added to the exhaust and the exhaust can be mixed well while maintaining a low pressure loss. Accordingly, an object of the present invention is to provide an exhaust treatment device including a selective reduction catalyst device that can effectively reduce and purify a specific component (for example, NOx) in exhaust gas.

Therefore, the exhaust treatment device according to the present invention is
An exhaust treatment device for treating exhaust gas discharged from a combustion device,
A selective catalytic reduction device that reduces and purifies specific components in the exhaust; and
A reducing agent addition device for adding a reducing agent to the exhaust on the exhaust upstream side of the selective catalytic reduction device;
In those with
Between the reducing agent addition device and the selective catalytic reduction catalyst device, a large number of members are disposed substantially evenly over the entire cross section substantially perpendicular to the exhaust flow in the exhaust passage and extend in the direction along the exhaust flow . While interposing a metal structure having a passage without restricting the exhaust passage,
A selective reduction catalyst is supported on the metal structure, and
At least some of the passages of the metal structure are communicated with each other,
The selective reduction catalyst device is a urea selective reduction type NOx catalyst device, and a catalyst device or a particulate filter is disposed on the exhaust upstream side of the reducing agent addition device.

  According to the present invention, the reducing agent added to the exhaust gas and the exhaust gas can be well mixed while maintaining a low pressure loss while being a simple, compact, and inexpensive configuration, and thus effectively in the exhaust gas. It is possible to provide an exhaust treatment device equipped with a selective catalytic reduction device that can reduce and purify specific components (for example, NOx).

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

As shown in FIG. 1, an exhaust treatment apparatus according to an embodiment of the present invention is an oxidation catalyst in terms of regeneration efficiency and the like at a relatively high exhaust temperature position on the most upstream side of an exhaust passage 2 of a diesel combustion engine 1. A device 3 and a diesel particulate filter 4 (or any one of them) may be interposed, and a urea water addition device 5 and a urea SCR catalyst device 6 (for example, a ceramic material such as cordierite as a carrier) on the downstream side thereof ), And an ammonia oxidation catalyst device 7 for oxidizing excess ammonia (NH ₃ ) leaking from the urea SCR catalyst device 6 is interposed.

  The urea water adding device 5 is stored in a urea water injection nozzle 5A that supplies urea water to exhaust gas at a predetermined timing, a urea water tank 5B that stores urea water, and the urea water tank 5B. And a supply pump 5C for supplying and supplying urea water with a predetermined pressure to the urea water injection nozzle 5A. However, the urea supply method is not limited to this.

  In the present embodiment, like the conventional exhaust treatment device shown in FIG. 8, a large-diameter housing case 8 for housing the oxidation catalyst device 3 and the diesel particulate filter 4, the urea SCR catalyst device 6 and ammonia. Without adopting a configuration in which the small-diameter exhaust passage 2A with a small exhaust passage cross-sectional area is provided between the large-diameter housing case 9 for housing the oxidation catalyst device 7, the oxidation catalyst device 3 and the diesel particulate filter 4 are provided. The large-diameter accommodating portion 10 to be accommodated is connected to the large-diameter accommodating portion 11 that accommodates the urea SCR catalyst device 6 and the ammonia oxidation catalyst device 7 through a connecting portion 12 that connects these diameters while maintaining their diameters substantially. It is supposed to be.

It is also possible to adopt a housing case in which the housing portion 10, the housing portion 11, and the connection portion 12 are formed substantially integrally.
Here, the accommodating portion 10, the accommodating portion 11, and the connecting portion 12 can be formed of a metal member, and various materials such as steel, SUS, Ti, and the like can be employed.

  Thus, in the present embodiment, since the exhaust passage 2A having a small diameter is not provided as in the prior art, the housing portion 10 and the housing portion 11 are connected via the large diameter connecting portion 12, Since there is no portion (throttle portion: small-diameter exhaust passage 2A) in which the exhaust passage cross-sectional area is reduced, pressure loss can be kept low.

  In addition, as shown in FIG. 1, if the storage portion 10 and the storage portion 11 are connected via the large-diameter connection portion 12 as in the present embodiment, the exhaust passage cross-sectional area is reduced. Since there is no need for the part to be expanded (squeezed part / expanded part), for example, it is sufficient to secure the minimum length necessary to secure the time required for hydrolysis from urea to ammonia. Thus, the length of the exhaust treatment device in the exhaust flow direction can be shortened, which can contribute to reduction in size, weight, and cost.

  In the present embodiment, it is possible to adopt the above-described configuration because a metal is disposed on the downstream side of the urea water injection nozzle 5A disposed in the connecting portion 12 and on the upstream side of the urea SCR catalyst device 6. This is based on the arrangement of the catalyst 20.

The metal catalyst 20 is configured by applying and supporting a urea SCR catalyst by coating or the like on the surface of a metal honeycomb structure carrier having cells that are a large number of passages formed of SUS or the like.
For example, as shown in FIG. 2, the carrier of the metal catalyst 20 can be formed by spirally winding a corrugated member 21 and a plate-like member 22 formed into a corrugated shape made of metal. . The plate-like member 22 can be constituted by a metal plate having a large number of holes and slits, a porous fiber member, and the like. Further, the plate-like member 22 can be omitted.

Then, exhaust flows through the passage (cell) 23 formed by the wave shape, flows out downstream, and flows into the urea SCR catalyst device 6 disposed on the exhaust downstream side of the exhaust passage 2. .
The metal catalyst 20 may be a catalyst using a honeycomb structure in which metal plate-like members 22 are joined in a lattice shape as a carrier.
Further, as shown in FIG. 3, the metal catalyst 20 may be a catalyst using a honeycomb structure in which metal pipe-like members 24 are arranged in bundles to form passages (cells) 23 as a carrier. it can.

Here, the metal catalyst 20 is easily affected by the exhaust temperature because the carrier is made of metal, and follows the change in the exhaust temperature well. Therefore, the metal catalyst 20 receives the heat of the exhaust gas passing through the metal catalyst 20 and has a short carrier temperature. In addition, since the surface area is large, the hydrolysis of urea into ammonia is promoted and gasification is promoted. Therefore, the mixing of the exhaust gas and the reducing agent added to the exhaust gas is performed by the mixer. It will be promoted compared to the prior art with such as.
For this reason, the NOx reduction efficiency in the urea SCR catalyst device 6 can be effectively increased.

Moreover, since the urea SCR catalyst is supported on the surface of the metal catalyst 20 according to the present embodiment, as described above, when hydrolysis of urea into ammonia is promoted and gasification is promoted, Even on the metal catalyst 20, NOx in the exhaust is reduced.
Therefore, compared with the case where a mixer or the like is used as in the prior art, when the same urea SCR catalyst 6 is employed, the urea SCR catalyst carrying area can be increased, so that the NOx purification efficiency can be increased.

Furthermore, when the metal catalyst 20 as in the present embodiment is provided, the following operational effects can also be achieved.
That is, the metal catalyst 20 is made of a metal and is easily affected by the exhaust temperature, and follows the change in the exhaust temperature well. Therefore, the metal catalyst 20 easily rises in temperature during cold start or the like. Compared with the case where only the urea SCR catalyst device 6 supporting the SCR catalyst is provided, it is possible to purify the NOx in the exhaust from an early stage after the start.

  In addition, after warm-up, for example, when the engine is shifted to an operating state in which the exhaust temperature of the diesel combustion engine 1 is lowered, the metal catalyst 20 is made of metal and is easily affected by the exhaust temperature. Therefore, if the exhaust gas temperature decreases, the amount of heat released from the metal catalyst 20 (the amount of heat removed by the exhaust gas) increases, so that the urea SCR catalyst device 6 on the downstream side The inlet temperature is maintained to be high, and therefore, the influence of the lowering of the exhaust temperature compared to the case where only the urea SCR catalyst device 6 in which the urea SCR catalyst is supported on ceramic such as cordierite is provided. Therefore, after the exhaust gas temperature is lowered, the NOx purification action in the exhaust gas can be maintained for a longer time.

In addition, for example, in the case where the exhaust temperature of the diesel combustion engine 1 shifts to an operating state where the exhaust temperature rises relatively rapidly, the metal catalyst 20 is made of metal and is easily affected by the exhaust temperature. In order to follow the change well, when the exhaust temperature is going to rise, the metal catalyst 20 takes heat from the exhaust, and the temperature of the metal catalyst 20 rises relatively rapidly. Therefore, since the rapid temperature rise of the urea SCR catalyst device 6 on the exhaust gas downstream side of the metal catalyst 20 can be suppressed, performance deterioration of the urea SCR catalyst 6 and damage due to heat can be suppressed. The purifying action of NOx in the exhaust gas can be maintained over a long period of time.
In other words, by arranging the metal catalyst 20 on the upstream side of the urea SCR catalyst device 6, the exhaust temperature flowing into the urea SCR catalyst device 6 can be stabilized, and the NOx reduction efficiency in the urea SCR catalyst device 6 can be improved. It can increase effectively and can improve reliability.

In the present embodiment, the case where the metal catalyst 20 supporting the urea SCR catalyst is disposed has been described. However, the present invention is not limited to this, and a catalyst such as a urea SCR catalyst is supported. It is possible to promote the above-described hydrolysis of urea to ammonia and thereby promote gasification even by disposing a metal honeycomb structure that is not present, so that it is added to the exhaust gas and the exhaust gas. The mixing with the reducing agent can be promoted as compared with the prior art equipped with a mixer or the like. Furthermore, it is possible to contribute to stabilization of the inlet temperature of the urea SCR catalyst device 6 disposed on the exhaust downstream side described above.
Therefore, the NOx reduction efficiency in the urea SCR catalyst device 6 can be effectively increased only by disposing a metallic honeycomb structure that does not carry the urea SCR catalyst.

Incidentally, the pipe-shaped member 24 constituting the metal catalyst 20 shown in FIG. 3 is provided with, for example, a notch 24A as shown in FIG. 4 (a), or a communication hole as shown in FIG. 4 (b). By providing 24B or providing the communication hole 24B and the partition plate 24C as shown in FIG. 4C, the adjacent passages 23 can be in communication with each other. This configuration can be similarly applied to the corrugated member 21 constituting the metal catalyst 20 shown in FIG.
When such a cutout 24A and a communication hole 24B are provided, the exhaust flow is branched by the cutout 24A and the communication hole 24B as shown in FIGS. It flows into the passage 23 of the shaped member 24 and collides with the flow of exhaust in the passage 23 that has flowed in, so that the mixing of the exhaust and the reducing agent added to the exhaust can be further promoted, Accordingly, the NOx reduction efficiency in the urea SCR catalyst and the urea SCR catalyst device 6 on the metal catalyst 20 can be further increased.
Further, the communication hole 24B can be configured to have a bent portion 24D as shown in FIG.
In addition, as a metal catalyst 20 at the time of using the corrugated member 21, what is described in Japanese translations of PCT publication No. 2006-507445 etc. is also applicable, for example.

  By the way, in the present embodiment, the diesel combustion engine 1 has been described as an example. However, the present invention is not limited to this, and a combustion apparatus with exhaust gas is not limited to a gasoline engine or other internal combustion engines. A combustion engine can be used, and any mobile or stationary combustion device can be used regardless of the combustion method.

  Further, in the present embodiment, the example in which the urea SCR catalyst device 6 is employed and urea water is added as the reducing agent to the exhaust gas has been described. However, the present invention is not limited to this and flows through the exhaust passage 2. The present invention can be applied to an exhaust treatment apparatus that is required to add a predetermined additive substance to the exhaust gas and to mix the additive substance and the exhaust gas.

  Each embodiment described above is only an example for explaining the present invention, and various modifications can be made without departing from the gist of the present invention.

It is a figure showing the example of whole composition of the exhaust-air-treatment device concerning one embodiment of the present invention. It is a figure which shows the structural example of the metal catalyst which concerns on embodiment same as the above. It is a figure which shows the other structural example of the metal catalyst which concerns on embodiment same as the above. It is a figure which shows the structural example of the pipe-shaped member used in the metal catalyst shown in FIG. It is a function explanatory view explaining the flow of exhaust at the time of using the pipe-shaped member which provided the communicating part. It is a function explanatory view explaining the flow of exhaust at the time of using a pipe-like member provided with a communicating part and a partition plate. It is function explanatory drawing explaining the flow of exhaust_gas | exhaustion at the time of using the pipe-shaped member which provided the communication part and the bending part. It is a figure which shows the structural example of the conventional exhaust processing apparatus. It is a figure explaining the reaction in each apparatus of the oxidation catalyst apparatus of a conventional exhaust gas processing apparatus, a urea water addition apparatus, a urea SCR catalyst apparatus, and an ammonia oxidation catalyst apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Diesel combustion engine 2 Exhaust passage 2A Small-diameter exhaust passage 3 Oxidation catalyst 4 Diesel particulate filter 5 Urea water addition device 5A Urea water injection nozzle 5B Urea water tank 5C Supply pump 6 Urea SCR catalyst 7 Ammonia oxidation catalyst 10 Large diameter accommodation Part 11 Large diameter housing part 12 Connection part 20 Metal catalyst (metal structure)
21 corrugated member 23 passage (cell)
24 Pipe-shaped member 24A Notch portion 24B Communication portion 24C Partition plate 24D Bent portion

Claims (1)

An exhaust treatment device for treating exhaust gas discharged from a combustion device,
A selective catalytic reduction device that reduces and purifies specific components in the exhaust; and
A reducing agent addition device for adding a reducing agent to the exhaust on the exhaust upstream side of the selective catalytic reduction device;
In those with
Between the reducing agent addition device and the selective catalytic reduction catalyst device, a large number of members are disposed substantially evenly over the entire cross section substantially perpendicular to the exhaust flow in the exhaust passage and extend in the direction along the exhaust flow . While interposing a metal structure having a passage without restricting the exhaust passage,
A selective reduction catalyst is supported on the metal structure, and
At least some of the passages of the metal structure are communicated with each other,
The exhaust gas treatment device, wherein the selective reduction catalyst device is a urea selective reduction type NOx catalyst device, and a catalyst device or a particulate filter is disposed on the exhaust upstream side of the reducing agent addition device.